1. Field of the Invention
The present invention relates in general to tool chucks for attachment of accessories to power drivers, and more particularly to a tool chuck having chuck jaws that may be actuated via power from the driver's transmission.
2. Description of Related Art
Commonly-assigned, provisional Application, entitled “TOOL CHUCK WITH POWER TAKE OFF AND DEAD SPINDLE FEATURES,” filed Apr. 19, 2005, and designated U.S. Application No. 60/672,503 (“the '503 application”), is hereby incorporated in its entirety by reference. The '503 application describes examples of a power driver that may be selectively operated in different modes, including a chuck mode. In the chuck mode, the driver may be powered up to actuate (i.e., open and close) the tool chuck. During chuck actuation, the chuck body and the chuck jaws may not rotate. This may be referred to as a “dead spindle” feature since the user may not be exposed to (or observe) any rotating parts.
Tool chucks may implement a sliding sleeve that may be selectively grounded (i.e., rotationally fixed) to the housing of the power driver. When the sleeve is grounded, the driver may be powered up to actuate the tool chuck. In some cases, the sleeve may selectively ground the chuck body to the housing of the power driver. Here, the chuck body and the chuck jaws may not rotate during chuck actuation, thereby affecting a dead spindle feature.
Conventional sliding sleeve tool chucks are generally thought to provide acceptable performance. However, if the chuck body is selectively grounded to the housing of the power driver and if the motor is run in the forward direction until the chuck jaws are tightened onto the accessory, then the motor may stall. The motor may also stall when the tool chuck is driven to a fully opened condition. Motor stall may damage the motor, damage the transmission and/or result in erratic tightening torques.
Various features have been developed in an effort to avoid the shortcomings noted above. For example, the power driver may implement an electronic clutch. Here, when the sliding sleeve selectively engages the housing of the power driver, the electronic clutch may be enabled to limit the applied torque to a desired tightening torque (during chuck actuation). Alternatively, the power driver's mechanical clutch, which typically limits the applied torque during a drill/drive mode, may be adapted to also limit an applied torque to a desired tightening torque (during chuck actuation).
The electronic and mechanical clutch features noted above are not without shortcomings. For example, power drivers may be equipped with multiple operating speeds. Unless the electronics can determine and compensate for the selected operating speed, then the torque delivered by the electronic clutch may vary during chuck actuation. The same may be true where the power driver's mechanical clutch serves to limit an applied torque to a desired tightening torque during chuck actuation.